


Automatic Assumptions

by tiamatv



Category: Supernatural
Genre: Alpha/Beta/Omega Dynamics, BAMF Castiel (Supernatural), BAMF Dean Winchester, Best Friends, Breakfast for dinner, Dean Winchester is So Done, Fluff, M/M, what happens when you assume
Language: English
Status: Completed
Published: 2020-05-18
Updated: 2020-05-18
Packaged: 2021-03-02 18:00:32
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,814
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24260983
Author URL: https://archiveofourown.org/users/tiamatv/pseuds/tiamatv
Summary: Everybody knew that Dean Winchester was an omega.It was the lips, some said, and the lashes. It was the way he looked so pretty when he smiled just out of the corner of his mouth, and the way his eyes lit up when he grinned. Sure, he was tall, broad-shouldered—yes, he worked with his hands. But what else could he be?"Uh-huh," said Dean.
Relationships: Castiel/Dean Winchester
Comments: 44
Kudos: 432





	Automatic Assumptions

**Author's Note:**

> Happy Monday, everybody! I needed a palate cleanser from the Mafia, and for some reason my brain wanted to write my first A/B/O and grouchy not-an-omega-dammit Dean? So here we are.
> 
> TRIGGER WARNING: there is discussion of a character in this (not one of our sweet boys) who was an asshole and hit on someone in an extremely inappropriate way.
> 
> \\\Laura, Queen of the Damned// [wearetheluckyones](http://www.archiveofourown.com/users/wearetheluckyones_Laura/pseuds/wearetheluckyones_Laura) did me the kind favor of betaing this (and I am so, so sorry I made you splutter in public. Okay, not that sorry.)

Everybody knew that Dean Winchester was an omega.

It was the lips, some said, and the lashes. It was the way he looked so pretty when he smiled just out of the corner of his mouth, and the way his eyes lit up when he grinned. It was the pink of his tongue and the sweet, bright angle of his jaw. Sure, he was tall, broad-shouldered—yes, he worked with his hands. But what else could he be?

“Uh-huh,” Dean said, with a derisive flick of his fork. “Since I’ve never once made slick outta my ass, pretty sure what’s happening down below is more important than my eyelashes.”

Someone at the table behind them choked.

In front of him, Castiel didn’t _quite_ snort juice out his nose, but it was a near thing. “ _Dean,_ ” he chided, pressing his napkin to his full, pouty lips. Then one of his eyebrows tilted up—that well-concealed bit of badass sass that Dean was sort of secretly into—and he folded both hands in front of him like the nerd that he was. Castiel intoned, solemn and straight-backed, “Do we have to have the ‘no presentation at the diner table’ talk again?”

“Huh. _Is_ that a talk that we’ve had? Pretty sure I’d remember that,” Dean crunched a piece of bacon—or he would have, if it had been crunchy. He’d gotten vetoed on diner choice this time, and this was the last time he was letting Cas pick. Dean glared at the soggy piece of salted meat on his fork. Artisan, his fine slickless ass.

“If not, all of a sudden I feel like it’s a talk that we _should_ ,” Castiel told him, calm as ever. “Or maybe just the ‘please don’t mention slick while we’re eating’ talk.”

“Doesn’t make it any less true,” Dean grumbled.

Castiel gave him the eyebrow again. “Doesn’t make it any less _gross,_ Dean.” He went back to his breakfast-for-dinner with measured enthusiasm.

Dean shoveled hash browns into his mouth, and he guessed it was a sign of how annoyed he looked that Cas didn’t even say anything when he squirted enough ketchup on them to drown the Titanic. “It just pisses me off,” he finally mumbled around a mouthful. “I’m not talking about slick, okay?” he waved a fork when Cas gave him a suspicious look. “It’s just… why’s everyone think that about me?” he gestured up and down his body with the fork. “I mean, what’s the point?”

Castiel’s eyes narrowed, just slightly. “What’s wrong with being an omega?” The hint of danger in his voice wasn’t cute, and it wasn’t the teasing eyebrow.

That was Cas for you, Dean guessed, and his lips curved in a reluctant smile at how Cas was low-key glaring at him. For a dorky little guy who didn’t quite seem to know how to dress himself properly, Cas had the whole protective alpha thing going to the _nines_. Dean was pretty sure no-one had ever mistaken Castiel Novak for an omega in his entire life—he’d _seen_ the kidlet pictures, Cas had had the same piercing stare even when he’d been cute as a fucking button and so little his eyes took up half of his face. But he was also pretty sure that if anyone ever did fudge Cas’s presentation, Cas would politely nod and say, _“You’re incorrect, but thank you for thinking so.”_

“Nothing!” Dean reached over and stole one of Castiel’s sausage links, but Cas didn’t jab him with his fork, so Dean knew he was letting him. “Nothing’s _wrong_ with it. I get it. I mean, the heats sound like they suck, but getting to have babies is the tradeoff, right? And all the caretaking and responsibility and all that shit. And that’s great, except for the fact that _I ain’t one._ ”

“Dean, you _do_ take good care of people,” Castiel told him, so fucking earnest Dean didn’t know whether he was poking fun or…

No, it was Cas, he really wasn’t.

Dean scowled at him. “Not helping.”

Castiel cut his pancakes into neat quarters, then considered Dean’s expression and relocated half of a pancake to Dean’s plate, taking one of the bacon pieces that were offending Dean right now in exchange. “What happened?”

Dean stabbed the pancake a little too hard, and his fork skidded across the plate with a screech that made him wince. “Just some guy last night. Started talking about my pretty face,” he muttered, going gentler with the cutlery. Dean didn’t mind being told he was good-looking; he got that all the time. Got it from guys and girls, alpha, beta and omega. Most of the time it got him just what he wanted, but then there were days like last night. “Tried to tell me ‘bout how he wanted to knock me up on his knot and keep me gentle under his hand.”

Then he’d tried to put a hand on the back of Dean’s neck and sniff him, all while Dean was still staring at him open-mouthed and horrified on behalf of an entire _presentation class._ Dean had never in his life been _so glad_ that he _wasn’t_ an omega, whose biological instincts would have made them go soft for that sort of hands-on bullshit whether they wanted it or not.

Or maybe not, what did Dean know? He was pretty sure there was no amount of instinct and neck-touching and presentation hormones that would have kept him from swatting the creep’s hand away.

Punching the asshole when he didn’t get the message the first time and reached out for Dean’s nape _again_ was probably excessive, but Dean didn’t regret it. Fucking _knothead_.

“ _Dean_.” Castiel’s hand landed on Dean’s forearm. He _squeezed_. Dean looked up from his food.

Dean’s ruffled raven of a best friend was solid and pretty on a good day and just sort of disheveled on a bad one. He was polite and awkward and he did things like eat pizza with a knife and fork. He made like a tiny little black-haired budgie when he didn’t understand a pop culture reference, he had a collection of board games, and he did jigsaw puzzles in his spare time.

He was also a fucking _scary_ sonofabitch when he wanted to be, putting out aggression like he grew it in his basement.

Cas didn’t go hot—he never did, which was the most impressive thing that Dean thought he’d ever seen. He didn’t lose control. He straightened his back and lifted his chin, went cold and sharp, no longer small and cute and pouty-mouthed, and his eyes were like the flick of a cobalt razor. Anyone with sense backed away from Castiel Novak when he rose alpha like that.

Dean did not have any sense, so there was that.

“That’s not alright,” Castiel told him, furious and dangerous and _gorgeous_. “It wouldn’t be alright if you’d been an omega, and it’s not alright regardless of whether you are a beta or an alpha, or _whatever_ you are.”

Dean blinked, momentarily startled out of the simmer of his own anger by the depth of Cas’s rage. That wasn’t too much different from anything that he’d expected Cas to say, but… “Wait.” Cas was an alpha and they spent a lot of time together, so Dean had always thought that Cas would be able to _smell_ that Dean didn’t have a presentation scent. But Cas was also very polite about that, and Dean didn’t think he’d ever seen him even sniffing air, much less sticking his head up against anyone’s neck. “You don’t… know?”

“No. I don’t _care_ ,” Castiel answered in a way that made his deep voice twist into a _snarl_ , and… huh. He meant that. And huh. The sound of his voice rasping on those syllables made that familiar _something_ start up hot in the depths of Dean’s belly with its usual terrible timing. “You are _yourself_ , Dean. You are tough and you are amazing. You could be alpha, beta, omega, trans-presentation or _neuter_ , and you would still be yourself, and you would still deserve better than that.”

When Cas said things like that, Dean kind of forgot how he wasn’t supposed to have feelings for his best friend. It made it _really_ hard to shove down that warm curl of affection and heat that popped up when Cas went all protective. It made his breath go tangling in his throat before he swallowed it down, warm and sour.

While he was still getting ahold of himself, Cas huffed out a slow breath. “Did you hit him?” he growled, quieter now.

“Yeah.” Shit Dean really should not like the sound of that—the way Castiel’s hoarse bass rolled up and down like a purr when he was upset. “Hey.” Carefully, he patted the hand Cas had gripping his forearm. Castiel started, like he’d forgotten he had a hand there, and it made Dean smile a little. Alphas did the skin thing just as much as omegas did, just differently. “I’m okay. Thought you were against violence,” he teased, gently.

“I am.” Castiel moved his shoulders, back and forth, like he was stretching out muscles that had gone hard and tight, and clenched and unclenched his fists. His calluses scraped gently against Dean’s forearm, and Dean pressed down a slow shudder. He didn’t see Cas’s canines trying to drop, but then, he never _had—_ Castiel’s control was truly unreal. “But if he never puts his hand on another omega like that,” Cas finally rumbled, “it’s done its job better than words.”

“Amen, I guess,” Dean offered. He really didn’t feel bad about hitting the guy. Yeah, he’d broken the alpha asshole’s nose, and he _should_ have broken his fingers. The manager hadn’t even disagreed with him. “So maybe it’s good it happened to me and not someone else. I dunno.”

“I wouldn’t say that,” Castiel’s eyes were still narrowed, but he finally settled back into his chair and picked up his orange juice again. His hand lifting off Dean’s forearm left a cold spot behind, and Dean kept himself from looking down to see if there was even the slightest hint of a white mark. “It shouldn’t happen to _anyone_ , but I don’t want it happening to you, either. Even if you _do_ punch well.”

“Yeah… well, screw my pretty eyelashes, anyway,” and that almost got a tiny, startled squint of a smile out of Castiel. That did a lot more to help the unease skimming down Dean’s nerves than any of the whiskey he’d pounded last night. He blew out a long, slow breath, let himself settle, too.

They didn’t say anything, but it was pretty rare that they needed to. Dean finished the pancake half that Castiel had put on his plate. Silently, Cas relocated another half over. Dean slipped him the edge of the hash browns, the crispy part.

“I’m a beta, for what it’s worth,” Dean finally offered, lifting his mug. The coffee was still hot.

“Oh. Alright. Thank you for telling me.” Cas nodded, more slowly, and he settled back down into his skin. The badass had curled back in, and Dean’s curious little raven blinked up at him. He didn’t look surprised or displeased or anything by Dean’s announcement, just… like Cas. “I apologize for losing my temper, I just…”

“Dude, you don’t need to apologize for getting mad. _I’m_ still mad. That shit’s fucked-up.” Dean didn’t try for a smile, but one curved upwards anyway as Cas pursed his lips. “I mean, I’m glad that kind of thing doesn’t happen to you, but I’m pretty sure you’d just handle it even if it did.” Shit, he could barely imagine someone trying it, but the visual that was flickering at the corners of his mind was kind of glorious—Cas with shoulders back and chin out, eyes blazing nuclear, his best “ _do not fuck with me and there’s no ‘or else’ to it”_ riding his shoulders.

Castiel blinked at him, very slowly, like the ocean peeking over the horizon on a long drive to the coast. “Why would you say that?”

This time, Dean did chuckle, finishing off his coffee with a swig. “Dude, you’re about as alpha as they come.” He shrugged. “No-one’d _ever_ be stupid enough to pull that presentation dominance bullshit with you.”

Cas was still blinking at him. “Sometimes they try,” he answered, to Dean’s startlement, but he still looked confused, squinting like someone trying to read a menu without their glasses on. “I don’t let them, but they try. Dean, I’m not.”

Dean poked the ketchup-soaked center of his hash browns absently. “You’re not…?”

Cas’s head tilted to the side. “Alpha.”

Dean’s brain twisted into a pretzel, tried to disentangle, then broke into a few oddly shaped pieces strewn on the diner floor, unable to rearrange. He looked back up so hard his chair scraped. “Wait… what?” he answered, stunned. Checked his gut. Nope, still attracted. “Aren’t you?”

“No.” There was the eyebrow. “I’m a beta.”

Oh shit, _oh shit_. “ _Fu-uck_ ,” Dean breathed, shaken by himself. “Cas, holy shit, I’m sorry, I didn’t—" he reached out before he realized that even if he’d just wrong-stepped like _fuck_ considering the topic of conversation, putting his hand on his best friend’s was going to come off weird. Even if he wanted to. Even if he’d wanted to reach across and grip his palm and feel his calluses, more than once. “I didn’t mean it like that, I just thought—"

Castiel raised his chin and blinked, slow and deliberate, like he was reminding Dean with nothing more than the expression on his face that time hadn’t stopped and that it was okay for him to breathe. His hand didn’t move from where Dean had grabbed it.

See, it was shit like _that_ that had always made Dean _very fucking certain_ that Castiel Novak was not an omega… but he’d never once thought that Cas was a beta. He’d never for an instant thought that Cas was the same as _Dean_. For very specific reasons. Well, one very specific reason.

“No apologies necessary. I don’t mind. Why would you think I was, though?” and Castiel didn’t sound annoyed, and he didn’t sound angry, and Dean could almost hear the echo of the _‘you’re mistaken but thank you_ ’ that he’d always imagined in it. “I know I can be a little… protective…”

A little? _Hah!_

“…but I don’t recall ever doing anything that would make you think I was going into rut, or sniffing for scent, or about to drop canines.”

His thoughts were circling his brain so fast that Dean couldn’t keep his mouth closed around them.

“’Cause I’m only attracted to alphas,” Dean blurted, helplessly.

Castiel’s eyes went wide.

*_*_*_*

Everyone knew that Dean Winchester was an omega.

Which was all pretty fucking stupid. Yeah, he had a nice face, and yeah, he had nice lips, and yeah, he knew what he liked to do with them. But none of that changed the fact that Dean was a beta and proud, and if he needed to get a t-shirt that said it and wear it _every day_ , then he was gonna. The next time someone tried to touch his neck they were gonna be pulling back a stump.

Everyone knew that Castiel Novak was an alpha.

Which just went to show that Dean really was just as much of a dumbass about presentation as everyone else was.

He didn’t know what he’d been thinking, because when he peeled Cas out of his ill-fitting clothes Cas was so _perfect_ just as he was, jaw-droppingly awesome, smooth cock and sleek body and all. When Dean felt the way Cas fit so _good_ in his body, the way he slid so easy once they got Dean all stretched and slick with lube, the way he could go slow _forever_ without an alpha drive to rut and mate… Dean couldn’t even remember why he’d liked a knot in him at all.

Then Cas pressed him gently against the wall, bit just under Dean’s ear, and guided Dean’s hand to the rise of his pert ass. He whispered “ _Do you want to try it the other way today?”_ like a mixed drink of sin, and holy fuck, _holy fuck_.

Even now, sometimes Cas just looked at him with his head tilted a little to the side and a possessive little smile, and that was all it took. Even when they were in public Dean’s mouth went dry and his pants got uncomfortably tight in a way they hadn’t for _any_ alpha he’d ever laid eyes upon.

Maybe it hadn’t been the head up top that had been doing any of Dean’s thinking. Or maybe it had been something else.

 _Everybody_ knew that Dean loved the Hell out of Cas.

Well.

Okay, yeah.

That one was true.

~fin~

**Author's Note:**

> So... my favorite A/B/O is the atypical kind, as you might have gathered. ;) This is the most fun I've had writing something in a long time! I didn’t want to tag their presentations because, well, it would have defeated the point—I hope no-one was too unpleasantly surprised!


End file.
